VERITAS Volume Manager 3.5 Installation Guide (August 2002)

Protecting Your System and Data
66 VERITAS Volume Manager Installation Guide
Protecting Your System and Data
VxVM can protect your system from loss of data due to disk failure.
The following are suggestions for protecting your data:
◆ Use mirroring to protect data against loss from a disk failure. To preserve data, create
and use mirrored volumes that have at least two data plexes. The plexes must be on
different disks. If a disk failure causes a plex to fail, the data in the mirrored volume
still exists on the other disk.
When you use the vxassist mirror command to create mirrors, it locates the
mirrors so the loss of one disk does not result in a loss of data. By default, the
vxassist command does not create mirrored volumes; edit the file
/etc/default/vxassist to set the default layout to mirrored. For information on
the vxassist defaults file, see the VERITAS Volume Manager Administrator’s Guide
and the vxassist(1M) manual page.
◆ Leavethe VxVMhot-relocationfeature enabled todetectdisk failuresautomatically. It
will notify you of the nature of the failure, attempt to relocate any affected subdisks
that are redundant, and initiate recovery procedures. Configure at least one
hot-relocation spare disk in each disk group. This will allow sufficient space for
relocation in the event of a failure.
If the root disk ismirrored,hot-relocation canautomatically createanother mirrorof
the root disk if the original root disk fails. The rootdg must contain enough
contiguous spare or free space for the volumes on the root disk (rootvol and
swapvol volumes require contiguous disk space).
◆ Use the Dirty Region Logging (DRL) feature to speed up recovery of mirrored
volumes after a system crash. Make sure that each mirrored volume has at least one
log subdisk.
Note usr volumes cannot be DRL volumes.
◆ Use logging to prevent corruption of recovery data in RAID-5 volumes. Make sure
that each RAID-5 volume has at least one log plex.
Perform regular backups to protect your data. Backups are necessary if all copies of a
volume are lost or corrupted. Power surges can damage several (or all) disks on your
system. Also, typing a command in error can remove critical files or damage a file
system directly. Performing regular backups ensures that lost or corrupted data is
available to be retrieved.